KR20030091974A - SOx TOLERANT NOx TRAP CATALYSTS AND METHODS OF MAKING AND USING THE SAME - Google Patents

Abstract

The present invention relates to sulfur tolerant catalyst composites useful for reducing contaminants in exhaust gas streams, especially gaseous streams containing sulfur oxide contaminants. More specifically, the present invention relates to an improved NOx trap catalyst for use in diesel engines and lean burn gasoline engines. The sulfur tolerable NOx trap catalyst composite comprises a platinum component, a support and a NOx adsorbent component prepared by NOx hydrothermal synthesis. The NOx adsorbent component includes a first metal oxide and a second metal oxide. The metal in the first metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is a Group IIA metal, Group III metal, Group IV metal, rare earth metal and transitions. It is selected from the group which consists of metals. The metal in the first metal oxide is different from the metal in the second metal oxide. Sulfur tolerant NOx trap catalyst complexes are very effective for sulfur containing fuels by trapping sulfur oxide contaminants that tend to poison the conventional NOx trap catalyst. Sulfur tolerable NOx trap catalyst composites are particularly suitable for diesel engines because the composites can be regenerated at intermediate temperatures with higher pulses than high temperatures.

Description

SOX TOLERANT NOx TRAP CATALYSTS AND METHODS OF MAKING AND USING THE SAME}

Diesel powered vehicles represent a significant part of the global vehicle market. In Europe, the diesel passenger vehicle market share is about one third, and is expected to grow higher over the next few years. Compared to gasoline powered vehicles, diesel vehicles provide better fuel economy and engine durability. As diesel passenger vehicles are becoming more common in Europe and elsewhere, emission reductions are becoming an increasingly urgent problem. Indeed, Euro IV Phase Regulation (2005) requires a 50% reduction (0.25 g / km) of NOx emissions compared to Tier III (2000) levels (0.5 g / km). In some vehicles, engine improvements alone may be difficult to meet Euro IV NOx emission targets. It would be impossible to meet the Euro V NOx regulation (0.125 g / km) without highly efficient aftertreatment technology.

It is very difficult to reduce NOx from diesel exhaust. The 3-way catalyst technology, which is widely used in gasoline vehicles, is not available in diesel vehicles. Three-way catalysts require emissions of emissions near the stoichiometry, whether fuel rich or rich (lean) lean (oxidation), but diesel emissions are always fuel deficient. In the early nineties, the concept of NOx trap catalysts was explored for gasoline partial lean burn (PLB) engines, where NOx catalysts could track NOx in a lean environment and reduce it in a rich environment.

In order to apply the NOx trap concept to diesel passenger vehicles, some special problems related to diesel emission characteristics need to be solved. The exhaust gas temperature for light diesel vehicles is typically in the range of 100 to 400 ° C., which is lower than gasoline exhaust gas. Therefore, low temperature oxidation activity and reduction during rich spikes are crucial. One of the most difficult problems in applying this concept is the problem of reduced sulfur activity. The exhaust sulfur forms very strong sulphate on all basic metal sites, which prevents the formation of nitrates, leaving the catalyst ineffective in trapping NOx. As for other catalytic converters, thermal stability is another important problem for practical use.

The action of the NOx trap catalyst is a set of basic steps, which are shown in Schemes 1-5 below. In general, NOx trap catalysts should exhibit both oxidation and reduction functions. In an oxidizing environment, NO is oxidized to NO ₂ (Scheme 1), which is an important step for NOx storage. At low temperatures, the reaction is usually catalyzed by noble metals such as Pt. The oxidation process does not stop here. Further oxidation of NO ₂ to nitrate with the introduction of atomic oxygen is also a catalysis reaction (Scheme 2). Although NO ₂ is used as the NO x source, little nitrate is formed in the absence of precious metals. Precious metals have a dual function of oxidation and reduction. In the reducing role, Pt first catalyzes the release of NOx following the introduction of a reducing agent such as CO (carbon monoxide) or HC (hydrocarbon) (Scheme 3). It may recover some NOx storage sites but does not contribute to any NOx species reduction. The released NOx is then further reduced to gaseous N ₂ in the rich environment (Scheme 4 and 5). NOx emissions can also be induced by fuel injection, even with a net oxidizing environment. However, effective reduction of the released NOx by CO requires rich conditions. Since metal nitrate is more unstable at higher temperatures, temperature spikes can also cause NOx emissions. NOx trap catalysis is circulating. Metal compounds are believed to undergo primarily carbonate / nitrate conversion during lean / rich operations. The decrease in sulfur activity of the NOx trap catalyst is shown in Schemes 6 and 7. In Scheme 6, S occupies a site for NOx, and in Scheme 7 SOx replaces CO ₃ or NOx.

NO to NO ₂ Oxidation of Furnace

(1) NO + 1/2 O ₂ → NO ₂

NOx storage as nitrate

(2) ₂ NO ₂ + MCO ₃ + 1/2 O ₂ → M (NO ₃ ) ₂ + CO ₂

NOx emission

(3) M (NO ₃ ) ₂ + 2CO → MCO ₃ + NO ₂ + NO + CO ₂

N ₂ NOx to the furnace

(4) NO ₂ + CO → NO + CO ₂

(5) 2NO + 2CO → N ₂ + 2CO ₂

SO ₂ Deactivation Process

(6) SO ₂ + 1 / 2O ₂ → SO ₃

(7) SO ₃ + MCO ₃ → MSO ₄ + CO ₂

In Schemes 2, 3 and 7, M represents a divalent metal cation. M may also be a monovalent or trivalent metal compound, in which case the above schemes need to be balanced again.

A comparative study of the current most discussed Lean Burn DeNOx technologies, including non-continuously operated NOx adsorption techniques, as well as continuously operated selective catalytic reduction (SCR) techniques of V, Pt, and Ir, is proposed Euro III / IV. In light of the regulations, the latter technique represents the most promising comprehensive practice for NOx, HC and CO. Sulfur concentrations have a decisive effect on the long-term activity of NOx adsorber catalysts, and in the worst case studies, the use of low sulfur fuels does not prevent the accumulation of sulfur on NOx adsorber catalysts. Sulfur accumulation on the catalyst is neutralized by an engine induced desulfurization strategy, whereby sulfur is removed from the NOx adsorber catalyst. This requires reducing the exhaust gases at elevated temperatures for a short period of time. Optimization of desulfurization parameters is essential to inhibit the formation of H ₂ S. It is assumed that the thermal decomposition of the NOx adsorber catalyst proceeds through two different inactivation modes. The first one is based on the loss of Pt dispersion and is accelerated by the presence of oxygen, while the second one can back to the reaction between the NOx storage component and the porous support material. See Wolfgang Strehlau et al., Conference "Engine and Environment" 97.

Direct injection techniques for diesel engines and gasoline engines are the most desirable way to reduce future CO ₂ emissions. NOx adsorber technology for gasoline DI engines and HSDI diesel engines is the preferred technology to meet future emission limits. Adsorbent catalysts have demonstrated the ability to meet future emission regulatory levels for samples for gasoline and diesel engines. The incorporation of adsorbent systems into motors for the improvement of NOx adsorbent technology and its introduction into the European market is a near future challenge.

Using a catalyst cannot reduce many NOx contaminants under lean burn conditions. Reduction of NOx by catalyst is very difficult in lean (oxidation) environment. To date, the use of any known catalyst (other than NOx traps) has achieved only very low conversion percentages. In order to convert NOx to N ₂ , a reducing atmosphere is required. Normal operating conditions for diesel or lean burn engines are not in a reducing atmosphere, but always lean (oxidation) engines exhaust gases. Under these lean conditions, NOx leaves little or no reduction and exits through the exhaust gas as a contaminant.

The NOx trap traps (adsorbs) NOx in a lean environment so that the NOx is removed from the exhaust gas stream. However, if a trap of limited capacity is consumed, NOx can no longer be trapped. NOx traps are only useful if they can be regenerated. For example, barium oxide can be used as a renewable NOx trap. In a lean (oxidative) environment, barium oxide continuously traps NOx and forms nitrates until capacity is consumed. To regenerate the trap, the gas stream is converted to rich (reduced) for a short time when NOx is rapidly desorbed from the trap, and the trap is regenerated back to barium oxide. Engine treatment or hydrocarbon injection can be used to create the rich environment. After regeneration, the NOx trap recovers full capacity (ideally) like a new trap. Thus, ideal NOx traps operate continuously in alternating lean / rich environments.

During the regeneration (rich) period, NOx is released, but no exhaust gas is released as contaminants. Since the catalyst is used in conjunction with the trap, the released NOx is reduced to N ₂ in a reducing (rich) environment. Thus, in the regeneration period, not only is the NOx trap regenerated, but the released NOx is converted to harmless N ₂ and CO ₂ .

If SOx does not appear in the gas stream, many NOx traps, including barium oxide, work well. Unfortunately, there is always SOx. Although the amount of SOx is much less than NOx (eg SOx: NOx = 1: 100), SOx can eventually deactivate the NOx trap. This is because SOx is a more powerful reactant than NOx. Once SOx is adsorbed on the site of the NOx trap, it sticks (forms a sulfate). SOx competes with the site for NOx, and the trap eventually deactivates. In addition, sulfided barium NOx traps can be regenerated (sulfide barium oxide requires higher temperatures to be regenerated than normal NOx regeneration processes).

The basic theory of hydrothermal synthesis and the apparatus used are described in "Hydrothermal Synthesis", George W. Morey, Journal of the American Ceramic Society, September 1, 1953. For example, the determination of the solubility of quartz in superheated streams at high temperatures and the determination of the composition of coexisting gas and liquid phases in a H ₂ O—Na ₂ O—SiO ₂ system at 400 ° C. are discussed.

Hydrothermal synthesis of lead titanate has been reported to involve the treatment of lead and titanium containing aqueous feedstock at temperatures in the range of 200 to 300 ° C. at autogenous pressure. Suitable sources of lead and titanium may be oxides derived from perchlorates, nitrates, acetates or alkoxides, or metal hydrate oxides. Hydrothermal synthesis of littitanate particles was studied using titanium isopropoxide and lead acetate. Two mechanisms are involved in the synthesis of lead titanate particles: 1) dissolution and then precipitation of the hydrous metal oxide feedstock, and 2) crystallization of the hydrous metal particles in the reactor, see “Hydrothermal Formation Diagram In the Lead. Titanate System "DJ Watson et al., Ceram. Trans, 1988, vol 1, Ceram. Powder Sci. 2 , Pt. A, 154-162.

The benefits of hydrothermal synthesis of Ba-polytitanate in the form of fine powders have been reported in connection with the use of microwaves. See "Hydrothermal precipitation and characterization of polytitanate in the system BaO-TiO ₂ " TRN Kutty et al., Journal of Materials Science Letters 7, 601-603 (1988).

US Patent No. 3,963,630 (Yonezawa et al.) Discloses a process for the preparation of crystalline powders of the composition represented by the formula PbTi _q Zr _p O ₃ . In the above formula, q and p represent molar ratios, the sum of q and p is 1.00, the molar ratio q is 0.45 or more and 0.90 or less, and the molar ratio p is 0.10 or more and 0.55 or less. The method comprises the steps of preparing an acidic aqueous solution of the metallic element at a molar ratio as shown in the formula, neutralizing the aqueous solution to provide a suspension of the hydroxide of the metallic element, the suspension having a mean particle size of 0.02 to 0.2 micron in the mother liquor of the composition. Placing under autoclave under pressure at a temperature of 150-300 ° C. for a time sufficient to produce a precipitate, and separating the precipitate from the mother liquor.

U.S. Patent 5,727,385 (Hepburn '385) discloses a catalyst system present in the exhaust gas passage of a lean-burn internal combustion engine useful for converting carbon monoxide, nitrogen oxides and hydrocarbons present in the exhaust gas. The catalyst system comprises two components: (1) consisting of copper, chromium, iron, cobalt, nickel, iridium, cadmium, silver, gold, platinum, manganese and mixtures thereof, which are loaded onto refractory oxide or exchanged for zeolite. Lean-burn nitrogen oxide catalyst, which is a transition metal selected from the group; And (2) a nitrogen oxide (NOx) trap material that adsorbs NOx when the exhaust gas flowing into the trap material is deficient and releases the adsorbed NOx when the oxygen concentration in the incoming exhaust gas is reduced. The nitrogen oxide trap material is located downstream of the lean-burn nitrogen oxide catalyst in the exhaust gas passage so that the exhaust gas is exposed to the lean-burn catalyst before it is exposed to the nitrogen oxide trap material.

U.S. Patent No. 5,750,082 (Hebburn et al., '082) discloses a nitrogen oxide trap useful for trapping nitrogen oxides present in the exhaust gas produced during lean-burn operation of an internal combustion engine. The trap may comprise (a) a porous support loaded with a catalyst comprising from 0.1 to 5 weight percent platinum; And (b) a different catalyst phase of another porous support loaded with 2-30% by weight of an alkali metal material selected from the group consisting of alkali metal elements and alkaline earth metal elements.

U.S. Pat.No. 5,753,192 (Dobson et al.) Traps nitrogen oxides present in the exhaust gas stream generated during the lean-burn operation of an internal combustion engine engine and adsorbs when the oxygen concentration of the exhaust gas is lowered. A nitrogen oxide trap useful for releasing nitrogen oxides is disclosed. The trap may comprise a porous support loaded with 6-15% by weight of strontium oxide; And (a) 0.5 to 5% by weight of a noble metal selected from platinum, palladium, rhodium and mixtures thereof loaded together thereon; (b) 3.5 to 15 weight percent zirconium; And (c) 15 to 30 weight percent of sulphate.

U.S. Patent 5,758,489 (Hepburn et al., '489) discloses a nitrogen oxide trap useful for trapping nitrogen oxides present in the exhaust gas produced during lean burn operation of an internal combustion engine engine. The trap comprises a porous support and a catalyst comprising at least 10 wt% lithium and 0.-4 wt% platinum loaded on the porous support.

US Pat. No. 5,759,553 (Lott et al.) Includes a NOx adsorbent material comprising activated alkali metal doped and copper doped hydrous zirconium oxide that adsorbs NOx under oxidation site geometry.

U.S. Patent 5,910,097 (Boegner et al.) Discloses an exhaust emission control system for an internal combustion engine. The system includes two adsorber portions arranged in parallel for alternating adsorption and desorption of nitrogen oxides contained in exhaust gas from the engine. Means for conducting exhaust downstream from one of the two adsorber sections currently operated adsorptively, and means for circulating exhaust gas from the other of the two adsorber sections detachably operated into the inlet line of the engine. Is provided. The oxidation converter is located upstream of the engine and at least from the adsorber portion for oxidizing NO contained in the exhaust gas to NO ₂ . The exhaust gas line zone is located upstream of the adsorber section and is divided into a mains basin and a barge basin parallel to the mains basin. The two adsorber sections are connected to the mains basin and the barge basin by a control valve so that one adsorptively actuated section is supplied with an exhaust stream from the mains basin and the other is a detachable actuator section with exhaust gas from the basin basin. The stream is fed.

European patent application 589,393A2 discloses a process for purifying oxygen-rich exhaust gas by simultaneously removing carbon monoxide, hydrocarbons and nitrogen tetrachloride contained in the exhaust gas. The method comprises (i) at least one precious metal selected from the group consisting of platinum and palladium, (ii) barium, and (iii) alkali metals, iron, wherein the exhaust gas rich in oxygen is supported on a carrier made of a porous material. And contacting with an exhaust gas purification catalyst comprising at least one metal selected from the group consisting of nickel, cobalt and magnesium.

EP 669,157 A1 discloses a catalyst for purifying exhaust gas. The catalyst comprises a heat resistant support; A porous layer coated on the heat resistant support; Noble metal catalyst components loaded on the porous layer; And a NOx storage component selected from the group consisting of alkaline earth metals, rare earth elements and alkali metals and loaded onto the porous layer. The precious metal catalyst component and the NOx storage component are disposed adjacent to each other and uniformly dispersed in the porous layer.

European patent application 764,459A2 discloses a nitrogen oxide trap useful for trapping nitrogen oxides present in the exhaust gas produced during lean-burn operation of an internal combustion engine. The trap may comprise (a) a first porous support loaded with a catalyst comprising 0.1 to 5 weight percent platinum; And (b) a different catalyst phase of the second porous support loaded with 2 to 30% by weight of a catalyst of a material selected from the group consisting of an alkali metal element and an alkaline earth metal element.

European patent application 764,460A2 discloses a nitrogen oxide trap useful for trapping nitrogen oxides present in the exhaust gas produced during the lean-burn operation of an internal combustion engine. The trap may comprise a porous support; And a catalyst consisting of manganese and potassium loaded on the porous support.

Laboratory and engine tests were performed to account for the sulfur effect on NOx adsorbent catalyst efficiency for gasoline lean burn engines. One aspect of the study dealt with the NOx storage efficiency of the adsorbent under laboratory conditions, especially with regard to the SO ₂ gas phase concentration. Sulfur storage rate is greatly affected by SO ₂ gas concentration. If the gas mixture contains 10 ppm SOx, it takes 6.5 hours to proceed to 75% NOx reduction to 35%, whereas it takes 20 hours with 5 ppm SOx and more than 60 hours with 2 ppm SO ₂ conditions. The relationship between loss of NOx trap performance and SO ₂ concentration appears to be exponential. The same amount of sulfur (0.8% weight) is deposited on the catalyst in 10 hours with a feed gas containing 10 ppm SO ₂ and within 50 hours with 2 ppm SO ₂ . Nevertheless, the loss of NOx-trap efficiency is not the same in both cases. The efficiency decreased from 70% to 25% in the first case (10 ppm SO ₂ ) and in the second case from 70% to only 38% (2 ppm SO ₂ ). The second aspect describes a study of parameters on the engine bench regarding the sulfur effect on NOx trap efficiency and the conditions (temperature, air / fuel ratio) needed to achieve different desulfurization rates. For example, after 70 hours, the NO x efficiency decreased from 90% to 25% with a sulfur content of 110 ppm gasoline. Complete regeneration requires various desulfurization durations depending on the air / fuel ratio (lambda = 1 to 0.95) and the temperature conditions (950 to 750 ° C.). For example, complete regeneration occurs after a few minutes at 650 ° C. at lambda = 1 and at 650 ° C. lambda = 0.95. The results indicate that the sulfur content close to the Euro III gasoline standards is a major obstacle for the introduction of NOx adsorbent catalysts in Europe. See Impact of Sulfur on Nox Trap Catalyst Activity Study of the Regeneration Conditions , M. Guyon et al., Society of Automotive Engineers, 982607 (1998).

Conventional catalysts described above using NOx storage components have the disadvantages of practical use which suffer from long term loss of activity due to reduced SOx activity of the NOx trap. Conventional NOx trap components used in catalysts tend to trap very SOx and form very stable sulfates that require regeneration at 650 ° C., which is not practical for low temperature diesel exhaust. Thus, developing a NOx trap catalyst that thermally traps the SOx present in the gaseous stream, thus preventing the NOx trap from deactivating SOx sulfur oxide activity and regenerating at intermediate temperatures with pulses higher than high temperatures. It is a continuous purpose.

This application is partly filed in US patent application Ser. No. 09 / 771,280, filed Jan. 26, 2001.

The present invention relates to sulfur tolerant catalyst composites useful for reducing contaminants in exhaust gas streams, especially gaseous streams containing sulfur oxide contaminants. More specifically, the present invention relates to an improved NOx trap catalyst for use in diesel engines and lean burn gasoline engines. The sulfur tolerable NOx trap catalyst composite comprises a platinum component, a support and a NOx adsorbent component prepared by NOx hydrothermal synthesis. The NOx adsorbent component includes a first metal oxide and a second metal oxide. The metal in the first metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is a Group IIA metal, Group III metal, Group IV metal, rare earth metal and transitions. It is selected from the group which consists of metals. The metal in the first metal oxide is different from the metal in the second metal oxide. Sulfur tolerant NOx trap catalyst complexes are very effective for sulfur containing fuels by trapping sulfur oxide contaminants that tend to poison the conventional NOx trap catalyst. Sulfur tolerable NOx trap catalyst composites are particularly suitable for diesel engines because the present composites can be regenerated at intermediate temperatures with higher pulses than high temperatures.

Summary of the Invention

The present invention

(1) providing a catalyst composite;

(2) the adsorber passes a lean gaseous stream comprising NOx and SOx through the catalyst complex within the adsorption temperature to adsorb at least some NOx contaminants to provide a NOx depleted gaseous stream exiting the catalyst complex, Adsorbing and mitigating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite;

(3) in the NOx desorption and alleviator, converting the lean gaseous stream into a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to provide a reduced NOx rich gaseous stream exiting the catalyst complex. step;

(4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream,

Wherein the catalyst complex is

(a) a platinum component;

(b) a support; And

(c) (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts which, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; And

(iii) is prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor,

The metal in the first metal oxide is selected from aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is from group IIA metals, group III metals, group IV metals, rare earth metals and transition metals. Wherein the metal in the first metal oxide comprises a NOx adsorbent component comprising a first metal oxide and a second metal oxide, different from the metal in the second metal oxide,

A method for removing NOx contaminants from a SOx containing gaseous stream.

The invention also

(i) providing a first metal oxide and a second metal oxide or a suspension or solution of precursors or both of the first and second metal oxides, which are metal salts that, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of;

(iii) separating the precipitate from the mother liquor; And

(iv) forming a mixture of precipitate, platinum component and support

It relates to a catalyst composite prepared by a hydrothermal synthesis method comprising a.

The invention also

(i) providing an aqueous suspension or solution of the first metal oxide and the second metal oxide or precursors of the first and second metal oxides, or both, which are metal salts which, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of;

(iii) separating the precipitate from the mother liquor; And

(iv) forming a mixture of precipitate, platinum component, and support.

The invention also

(1) (a) a support; And

(b) forming a mixture of NOx adsorbent components;

(2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid;

(3) forming a layer of a solution or dispersion on the substrate; And

(4) converting the platinum component in the obtained layer to a water insoluble form,

Where the NOx adsorbent component is

(i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; And

(iii) a method of forming a catalyst composite, which is prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor.

The sulfur tolerant NOx trap catalyst complex traps sulfur oxide contaminants in a lean environment where conventional NOx trap catalysts tend to deactivate, and releases sulfur oxide contaminants in a rich environment to regenerate NOx traps to the sulfur containing fuel. Very effective. Sulfur tolerant NOx trap catalyst composites are particularly suitable for diesel engines because the composites can be regenerated at intermediate temperatures with higher pulses than high temperatures.

In a preferred embodiment, the present invention

(1) providing a catalyst composite;

(2) the adsorber passes a lean gaseous stream comprising NOx and SOx through the catalyst complex within the adsorption temperature to adsorb at least some NOx contaminants to provide a NOx depleted gaseous stream exiting the catalyst complex, Adsorbing and mitigating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite;

(3) in the NOx desorption and alleviator, converting the lean gaseous stream into a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to provide a reduced NOx rich gaseous stream exiting the catalyst complex. step;

(4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream,

Wherein the catalyst complex is

(a) a platinum component;

(b) a support; And

(c) i) up to about 0.1% Na ₂ O;

ii) about 1% or less of MgO;

iii) about 10% to about 30% Fe ₂ O ₃ ;

iv) about 0.5% to about 15% SrO;

v) up to about 5% Y ₂ O ₃ ; And

vi) Al ₂ O ₃ components remaining from the NOx adsorbent composite,

(i) providing an aqueous suspension or solution of the NOx adsorbent component composition;

(ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And

(iii) a NOx adsorbent composite prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor.

A method for removing NOx contaminants from an SOx containing gaseous stream, comprising:

In another preferred embodiment, the present invention

(a) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor;

(c) separating the precipitate from the mother liquor; And

(d) a catalyst composite prepared by a hydrothermal synthesis process comprising the step of forming a mixture of precipitate, platinum component, and support.

In another preferred embodiment, the present invention

(a) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor;

(c) separating the precipitate from the mother liquor; And

(d) forming a mixture of precipitate, platinum component, and support.

In another preferred embodiment, the present invention

(1) (a) a support; And

(b) (i) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) forming a mixture of NOx adsorbent components comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid;

(3) forming a layer of a solution or dispersion on the substrate; And

(4) converting the platinum component in the obtained layer to a water insoluble form,

Where the NOx adsorbent component is

(i) providing an aqueous suspension or solution of the NOx adsorbent component composition;

(ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And

(iii) prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor,

A method for forming a catalyst composite.

Preferred NOx adsorbent components may further comprise from about 0.5% to about 15% BaO.

Detailed description of the invention and specific embodiments thereof

The present invention relates to sulfur tolerant catalyst composites useful for reducing contaminants in exhaust gas streams, especially gaseous streams containing sulfur oxide contaminants. More specifically, the present invention relates to improved NOx trap catalysts for diesel engines and lean burn gasoline engines. The sulfur tolerant NOx trap catalyst composite comprises a platinum component, a support, and a NOx adsorbent component prepared by hydrothermal synthesis. The NOx adsorbent component includes a first metal oxide and a second metal oxide. The metal in the first metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is a Group IIA metal, Group III metal, Group IV metal, rare earth metal and transitions. It is selected from the group which consists of metals. The metal in the first metal oxide is different from the metal in the second metal oxide. Sulfur tolerant NOx trap catalyst complexes are very effective for sulfur containing fuels by trapping sulfur oxide contaminants that tend to deactivate conventional NOx trap catalysts used to reduce other pollutants in the stream. Sulfur tolerant NOx trap catalyst composites are suitable for diesel engines because they can be regenerated at intermediate temperatures with pulses higher than high temperatures. Conventional NOx trap catalysts are readily deactivated by sulfur and cannot be ashed by high pulses below 650 ° C. Since the exhaust gas temperature of diesel engines is low, the temperature requirement above 650 ° C for regeneration is not practical. The sulfur tolerable NOx trap catalyst composites of the present invention can be regenerated with high pulses at moderate temperatures (up to 550 ° C). The present inventors found that when the NOx adsorbent component of the present invention is produced by hydrothermal synthesis, the obtained NOx adsorbent component is a fine crystalline powder (microparticles) having a sufficiently small average particle size so that the NOx adsorbent component is not produced by hydrothermal synthesis. It is believed that the regeneration (desorbing of SOx) is performed faster than the NOx adsorbent component.

Improved NOx trap catalysts are sulfur tolerant and can be used in sulfur-containing lean / rich environments for long periods of time. The accumulated sulfur in the NOx trap catalyst can then be released at temperatures readily reachable (eg 550 ° C. or less) under engine operating conditions. Thus, the NOx trap catalyst can be used continuously in a sulfur containing environment as long as it is periodically regenerated. If sulfur can be released under normal engine operating conditions, sulfur is automatically regenerated without additional effort, and the NOx trap catalyst becomes a completely sulfur resistant NOx trap.

The NO x trap material of the present invention is regenerated by hydrothermal synthesis to obtain ultrafine sub-micron mixed oxide composites. While not wishing to be bound by the mechanism, ultrafine sub-micron mixed oxides are believed to be more active than large (larger than 1 micron) bulk phase materials prepared by conventional methods. Furthermore, it is believed that the reducing agent regenerates new adsorption sites, where bulk oxides regenerate longer and nitrates and sulphates are adsorbed due to the more effective treatment of the surface and limited diffusion of rapid regeneration required. In diesel engines, the bulk NOx trap complex cannot remove sulfur in short regeneration cycles. Thus, it is rapidly deactivated. In contrast, oxides produced by the hydrothermal method are more effectively recycled.

The new SOx trap must be defeated before reaching the downstream NOx trap. However, all SOx traps have a limited capacity. There are many problems with using separate SOx traps with NOx traps. Higher temperatures are required to regenerate SOx traps, and released SOx in the gas stream must be prevented by deactivating downstream NOx traps, engine handling becomes more complex, and source reduction systems become complex. The present invention provides a trap that not only traps NOx and SOx, but also releases SOx so that some sites that track SOx are regenerated simultaneously when NOx is released during NOx regeneration. That is, SOx tolerant NOx traps may not require higher temperatures to be regenerated after sulfiding in an SOx environment. Additionally, no separate SOx traps are needed, and the NOx and SOx traps can be combined. Lean burn or diesel catalysts equipped with NOx / SOx traps can be regenerated similar to regeneration of simple NOx traps in sulfur-free environments.

With the SOx acceptable NOx trap of the present invention, it is possible to operate a source reduction system without the need for high temperature and / or individual SOx desorbers for SOx desorption. SOx tolerant NOx traps can also be operated continuously at intermediate temperatures (eg 300 ° C.) without temperature rise for trap regeneration (only lean / rich shifts are required).

The present invention includes a process for producing SOx acceptable NOx traps through the selection of suitable mixed oxides prepared by hydrothermal synthesis. After sulfidation, the SOx tolerant NOx trap can be fully regenerated at temperatures as low as 400 ° C. Barium oxide type NOx trap can be regenerated at the low temperature. After overall sulfidation for 68 consecutive hours (the amount of SOx passed is equal to the same amount of trap material), the NOx conversion was still effective. SOx tolerant NOx traps worked effectively without any temperature rise for trap regeneration (only lean / rich shifts are needed).

The catalyst adsorbs or traps NOx when the exhaust gas is a column and releases stored NOx when the exhaust stream is rich. The released NOx is subsequently reduced to N ₂ on the same catalyst. Rich environments in diesel engines are typically achieved with high pulses generated by engine operation or injection of a reducing agent (eg fuel or CO or CO / H ₂ mixture) into the exhaust pipe. The timing and frequency of high pulses is determined by the level of NOx emitted from the engine, the abundance of exhaust gas or the concentration of reducing agent in the high pulse and the required NOx conversion. Typically, the longer the lean period, the longer the rich pulse is needed. Longer rich pulse timing can be complemented by higher concentration of reducing agent in the pulse. Overall, the amount of NOx trapped by the NOx trap should be balanced by the amount of reducing agent in the rich pulse. Lean NOx trapping and rich NOx trap regeneration operate at normal diesel operating temperatures (150-450 ° C.). Beyond this temperature range, the efficiency of the NOx trap catalyst becomes less effective. In a sulfur containing exhaust stream, the catalyst is deactivated over time due to a decrease in sulfur activity. In order to regenerate the NOx trap deactivated with sulfur, a rich pulse (or pulses) must be applied at a temperature above the normal diesel operating temperature. The regeneration time of the production depends on the sulfur level (or fuel sulfur level) in the exhaust gas and the length of the catalyst is exposed to the sulfur containing stream. The amount of reducing agent added during desulfurization should be balanced with the total amount of sulfur trapped in the catalyst. Engine operability may determine whether a single long pulse or a plurality of short pulses are used.

As used herein, the following terms have the meanings defined below whether used in the singular or plural form.

The term "catalyst metal component" or "platinum metal component" or reference to a metal or metals comprising the same, or metal in a catalytically effective form whether the metal or metals are present in elemental form or in an alloy or compound (eg an oxide) Or metals.

The term “component” or “components” as applied to a NOx adsorbent is any effective NOx-trapping form of a metal, such as an oxygenated metal compound (eg, metal hydroxide, mixed metal oxide, metal oxide or Metal carbonate).

The term “composite” means a non-metal or multi-metal oxygen compound (eg Ba ₂ SrWO ₆ ) which is not only a true compound but also a physical mixture of two or more individual metal oxides (eg a mixture of SrO and BaO).

The term “dispersed,” as applied to a component dispersed on a bulk support material, means impregnating the bulk support material into a solution or other liquid suspension of the component or precursor thereof. For example, the adsorbent strontium oxide immerses bulk alumina in a solution of strontium nitrate (a precursor of strontium), dries the immersed alumina particles, and the particles are, for example, from about 450 ° C. to about 750 ° C. (calcined). The strontium nitrate can be dispersed on the alumina support material by heating in air at a temperature to convert the strontium nitrate to strontium oxide dispersed on the alumina support material.

The term "gas stream" or "exhaust gas stream" means a stream of gaseous constituents, such as the exhaust gases of an internal combustion engine, which may include entrained non-gaseous components such as liquid droplets, solid particulates and the like.

The terms "g / in ³ " or "g / ft ³ " used to describe weight units per volume describe the weight of the component per volume of the catalyst or trap member, including the volume that constitutes the void space, such as a gas-flow passage. do.

The term “lean” deficiency or treatment operation is such that oxygen in the gaseous stream being treated is more oxygen than the stoichiometric amount of oxygen required to oxidize the entire reducing agent component of the gaseous stream (eg, HC, CO and H ₂ ). It means to include.

The term "platinum group metal" means platinum, rhodium, palladium, ruthenium, iridium and osmium.

The term "adsorption" means to achieve sorption.

The term “stoichiometric / rich” modality or processing operation means that the gaseous stream being treated refers collectively to the gaseous stream of stoichiometric and rich operating conditions.

The term “washcoat” has the usual meaning in the art of a thin tacky coating of a catalyst or other material applied to a refractory carrier material, such as a honeycomb carrier member, which is porous enough to permit passage of the gas stream to be treated therethrough. .

According to the present invention, a method is provided for removing NOx contaminants from a SOx containing gaseous stream. The method comprises the steps of (1) providing a catalyst composite; (2) the adsorber passes a lean gaseous stream comprising NOx and SOx through the catalyst complex within the adsorption temperature to adsorb at least some NOx contaminants to provide a NOx depleted gaseous stream exiting the catalyst complex, Adsorbing and mitigating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite; (3) in the NOx desorption and alleviator, converting the lean gaseous stream into a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to provide a reduced NOx rich gaseous stream exiting the catalyst complex. step; (4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream. The catalyst composite may comprise (a) a platinum component; (b) a support; And (c) a metal in a first metal oxide selected from aluminum, titanium, zirconium, silicon and composites thereof, and a second selected from Group IIA metals, Group III metals, Group IV metals, rare earth metals and transition metals. A metal in the metal oxide, wherein the metal in the first metal oxide comprises a NOx adsorbent component that is different from the metal in the second metal oxide. The present NOx adsorbent component comprises: (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively. ; (ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; And (iii) separating the precipitate from the mother liquor.

In general, the SOx desorption temperature range is at least about 300 ° C., preferably the desorption temperature range is at least about 350 ° C., more preferably the desorption temperature range is at least about 400 ° C., and most preferably the desorption temperature range is about It is 450 degreeC or more. The SOx desorption temperature may also be at least about 500 ° C., preferably at least about 550 ° C., more preferably at least about 600 ° C. and most preferably at least about 650 ° C.

As noted above, the sulfur tolerant catalyst composite of the present invention comprises a platinum component, and optionally a platinum group metal component other than platinum. Platinum group metal components other than the optional platinum may be selected from the group consisting of palladium, rhodium, ruthenium, iridium and osmium components. Preferred platinum group metal components other than platinum are selected from the group consisting of palladium, rhodium and mixtures thereof.

The sulfur acceptable catalyst composite of the present invention also includes a support consisting of a high surface area refractory oxide support. The support may be selected from the group consisting of alumina, silica, titania and zirconia compounds. Useful high surface area supports include one or more refractory oxides. These oxides include silica and metal oxides such as alumina, including mixed oxide forms such as silica-alumina, aluminosilicate, which can be, for example, amorphous or crystalline alumina-zirconia, alumina-chromia, aluminum-ceria, and the like. . Preferably, the support is activated alumina, alumina-ceria, alumina-chromia, alumina-silica, alumina-zirconia, silica, silica-titania, silica-titania-alumina, silica-titania-zirconia, titania, zirconia, zirconia -Titania and zirconia-alumina-titania are activated compounds selected from the group consisting of: Preferably, the activated alumina has a specific surface area of 60 to 300 m ² / g.

The sulfur tolerant catalyst composite of the present invention also includes a NOx adsorbent component. The NOx adsorbent component includes a first metal oxide and a second metal oxide. The metal in the first metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon and composites thereof. The metal in the second metal oxide is selected from the group consisting of Group IIA metals, Group III metals, Group IV metals, rare earth metals and transition metals. The metal in the first metal oxide is different from the metal in the second metal oxide. Preferably the metal in the second metal oxide is manganese, calcium, strontium, barium, scandium, titanium, zirconium, hafnium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium , Ytterbium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. More preferably, the metal in the second metal oxide is selected from the group consisting of barium, lanthanum, cerium, iron, cobalt and copper. In specific embodiments, the metal in the first and second metal oxides is selected from the group consisting of aluminum / cerium / barium, aluminum / copper / lanthanum, aluminum / cobalt / lanthanum and iron / aluminum.

As noted above, the NOx adsorbent component is prepared by a hydrothermal synthesis process using an aqueous suspension or solution of the first and second metal oxides or precursors thereof or both. Precursors of the first and second metal oxides are metal salts which, when hydrolyzed, produce respective metal oxides. Preferred precursors of the first metal oxide and the second metal oxide are water soluble / minutes selected from the group consisting of acetate, nitrate, hydroxide, oxychloride, hydroxychloride, carbonate, sulfate, oxalate and tartrate Acid metal salts.

The metal in the first metal oxide and the metal in the second metal oxide are preferably about 3: 7 to about 9: 1, more preferably about 4: 6 to about 8.5: 1.5, most preferably about 5: each, respectively. Present in a ratio of 5 to about 7.5: 2.5.

As mentioned above, the NOx adsorbent component is produced by hydrothermal synthesis. In general, the method comprises the steps of: (i) providing an aqueous suspension or solution of two or more metal oxides or precursors thereof, wherein the precursors of the two or more metal oxides are metal salts that, when hydrolyzed, produce metal oxides of each metal oxide; (ii) from about 150 ° C. to about 300 ° C. in an autoclave under pressure for a time sufficient to produce a precipitate or solution of said at least two metal oxides or precursors thereof in the mother liquor having a mean particle size of from about 0.001 to about 0.2 microns. Adding a temperature of; And (iii) separating the precipitate from the mother liquor.

The suspension of the metal hydroxide is preferably subjected to a temperature of about 175 ° C to about 250 ° C, more preferably about 185 ° C to about 240 ° C. The precipitate preferably has an average particle size of about 0.01 to about 0.2 microns, preferably about 0.05 to about 0.15 microns.

In a preferred embodiment, the catalyst composite comprises (i) at least about 1 g / ft ³ of platinum component; (ii) a support of about 0.15 g / in ³ to about 6.0 g / in ³ ; And (iii) from about 0.025 g / in ³ to about 4 g / in ³ of the NO x adsorbent component.

The catalyst composite may be supported on a metal or ceramic honeycomb carrier or may be pressed independently.

The NOx adsorbent component may further comprise a third metal oxide, wherein the metal in the third metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is a second IIA. Group metal, group III metal, group IV metal, rare earth metal and transition metal. In this embodiment, the metal in the third metal oxide is different from the metal in the first and second metal oxides.

According to the present invention, the NOx adsorbent component is prepared by hydrothermal synthesis to obtain fine powder. At one time, the NOx adsorbent component may comprise providing an aqueous suspension or solution of the first and second metal oxides or precursors thereof or both; The suspension or solution of the first and second metal oxides or precursors thereof is about 150 ° C. to about 300 ° C. in autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to about 0.2 microns in the mother liquor. By applying a temperature of and separating the precipitate from the mother liquor.

The precursor solution / suspension is subsequently subjected to hydrothermal reaction with stirring to give a fine precipitate. The reaction can be carried out in an autoclave, preferably consisting of stainless steel coated with a heat resistant high polymer such as polytetrafluoroethylene. Precipitates prepared by hydrothermal reaction at temperatures of about 150 ° C. to about 300 ° C. generally have an average particle size of 0.001 to 0.2 microns. The precipitate can be separated from the mother liquor by filtration and then washing and drying.

In a preferred embodiment, the NOx adsorbent component provides (i) an aqueous suspension or solution of two or more metal oxides or precursors thereof, wherein the precursors of the two or more metal oxides are metal salts that, when hydrolyzed, produce each metal oxide. Doing; (ii) from about 150 ° C. to about 300 ° C. in an autoclave under pressure for a time sufficient to produce a precipitate having a mean particle size of about 0.001 to about 0.2 microns in mother liquor in a suspension or solution of the at least two metal oxides or precursors thereof. Adding a temperature of; And (iii) separating the precipitate from the mother liquor.

In use, an exhaust gas stream comprising air, water, hydrocarbons, carbon monoxide, nitrogen oxides and sulfur oxides, which are in contact with the catalyst composite of the present invention, are alternately adjusted and alternating between lean and stoichiometric / rich operating conditions. Operational periods and stoichiometric / rich operating periods are provided. The exhaust gas stream to be treated is subjected to lean or stoichiometric / rich conditions, respectively, by adjusting the air to fuel ratio supplied to the engine producing the exhaust gas, or by periodically injecting a reducing agent into the gas stream upstream of the catalyst. This can be optionally given. For example, the catalyst composite of the present invention is suitable for treating the exhaust gas of an engine, especially diesel engines that are continuously lean operated. In diesel engines, in order to establish the stoichiometric / rich operating period, a suitable reducing agent such as fuel is periodically sprayed into the exhaust gas immediately upstream of the catalyst trap of the present invention, at least locally (in the catalyst trap) at stoichiometric intervals. Provide rich conditions. Partial lean-burn engines, such as a partial lean-burn gasoline engine, are designed to be controlled to cause lean operation with short intermittent rich or stoichiometric conditions. In practice, the sulfur tolerant NOx trap catalyst complex adsorbs the incoming SOx during the lean aquaculture operation (100 ° C. to 500 ° C.) and the rich aquaculture operation (at least about 300 ° C., preferably at least about 350 ° C., more preferably about 400 SOx is desorbed (regeneration) in the middle of at least < RTI ID = 0.0 > The SOx desorption temperature may also be at least about 500 ° C, more preferably at least about 550 ° C, more preferably at least about 600 ° C, most preferably at least about 650 ° C. When the exhaust gas temperature is returned to the lean aquaculture operation (100 ° C. to 500 ° C.), the regenerated sulfur tolerant NO x trap catalyst composite may again selectively adsorb incoming SOx. The duration of the lean culture can be controlled such that the sulfur acceptable NOx trap catalyst complex cannot be saturated with SOx.

When the composition is applied as a thin layer coating to a single crystal carrier substrate, the component fraction is typically expressed in grams (g / in ³ ) of material per cubic inch of catalyst and substrate. These values accommodate different gas flow through cell sizes in different single crystal carrier substrates. The platinum group metal component is based on the weight of the platinum group metal.

Useful and preferred sulfur tolerant NOx trap catalyst composites include at least about 1 g / ft ³ of platinum component; A support of about 0.15 g / in ³ to about 4.0 g / in ³ ; Platinum group metal components other than platinum of at least about 1 g / ft ³ ; And from about 0.025 g / in ³ to about 4 g / in ³ NOx adsorbent component.

The specific construction of the catalyst composite reversibly traps the sulfur oxide contaminants present, thereby creating an effective catalyst that prevents sulfur oxide contaminants from deactivating NOx trap catalysts used in diesel engines. The catalyst composite may be in the form of an independently supported article such as pellets, more preferably the sulfur tolerant NOx trap catalyst composite is supported on a carrier (also referred to as a substrate, preferably a honeycomb substrate). . Typical so-called honeycomb carrier members include materials such as cordierite and the like, having a plurality of fine gas flow passages extending from the front portion to the rear portion of the carrier member. These fine gas flow passages, which can be about 100 to 900 passageways or cells per square inch of contact area, have catalyst trap material coated on their walls.

The invention also includes a process for treating an exhaust gas stream comprising contacting a gas stream comprising carbon monoxide and / or hydrocarbons, nitrogen oxides and sulfur oxides with a catalyst composite as described above. The invention also includes a process for treating an exhaust gas stream comprising contacting the stream under alternating lean and stoichiometric or rich operating periods with the catalyst composite as described above. The contacting is carried out under conditions in which at least a portion of the SOx of the exhaust gas stream is trapped in the catalytic material during the lean operation period and released and reduced during the stoichiometric or rich operation period.

In a specific embodiment, the present invention

(i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of;

(iii) separating the precipitate from the mother liquor; And

(iv) a catalyst composite produced by hydrothermal synthesis comprising the step of forming a mixture of precipitate, platinum component, and support.

The invention also

(i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of;

(iii) separating the precipitate from the mother liquor; And

(iv) forming a mixture of precipitate, platinum component, and support.

The invention also

(1) (a) a support; And

(b) forming a mixture of NOx adsorbent components;

(2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid;

(3) forming a layer of a solution or dispersion on the substrate; And

(4) converting the platinum component in the obtained layer to a water insoluble form,

Where the NOx adsorbent component is

(i) providing a first metal oxide and a second metal oxide or a suspension or solution of precursors or both of the first and second metal oxides, which are metal salts that, when hydrolyzed, produce metal oxides respectively;

(ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; And

(iii) a method of forming a catalyst composite, which is prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor.

Sulfur tolerant NOx trap catalyst complexes are very effective for sulfur containing fuels by trapping sulfur oxide contaminants that tend to deactivate conventional NOx trap catalysts used to mitigate other pollutants in the stream. Sulfur tolerable NOx trap catalyst composites are suitable for diesel engines because they can be regenerated at intermediate temperatures with higher pulses than high temperatures.

The sulfur tolerant catalyst composite may optionally include conventional components known in the art.

In order to deposit the coating slurry onto the macro-sized carrier, at least one ground slurry is applied to the carrier in any desired form. Thus, the carrier may be immersed one or more times in the slurry with intermediate drying, if necessary, until a suitable amount of slurry is present on the carrier. The slurry used to deposit the catalytically promoted metal component high region support complex on the carrier may often comprise 20 to 60 weight percent fine solids, preferably about 25 to 55 weight percent fine solids.

The sulfur acceptable carrier composite of the present invention can be prepared and applied to a suitable substrate, preferably a metal or ceramic honeycomb carrier, or pressed independently. The ground catalytically promoted metal component high region support complex may be deposited on the carrier in the desired amount, for example, the composite may be from about 2 to 40% by weight of the coated carrier, preferably from about 5 to 30% by weight of a conventional ceramic honeycomb structure. The composite deposited on the carrier is generally formed with a coating on most of the surface (if not all) of the carrier being contacted. The bonded structure may be dried and calcined, preferably at a temperature of about 250 ° C. or higher, but not so high as to unreasonably destroy high areas of the refractory oxide support unless desired under given conditions.

Carriers useful in the catalysts produced by the present invention may be metallic in nature and may consist of one or more metals or metal alloys. The metallic carrier can be in various shapes such as corrugated sheet or single crystal form. Preferred metallic supports include heat resistant, basic metal alloys, especially those in which iron is a substantial or major component. Such alloys may comprise one or more of nickel, chromium and aluminum, and the sum of these metals is advantageously at least about 15% by weight or more of alloys, such as about 10-25% by weight of chromium, about 3-8 Aluminum by weight and 20% by weight or less of nickel, or when present in trace amounts or more, about 1% by weight or more of nickel. Preferred alloys may include small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium, and the like. The surface of the metal carrier may be oxidized at significant elevated temperatures (eg, above about 1000 ° C.) to improve the erosion resistance of the alloy by forming an oxide layer on the carrier surface having a thicker and higher surface area than that obtained from ambient temperature oxidation. have. Provision of an oxidized or extended surface on the alloy carrier by high temperature oxidation can improve the adhesion of the refractory oxide support and the catalytically promoted metal component to the carrier.

Any suitable carrier may be used, for example, a single crystal carrier of the type having a plurality of fine parallel gas flow passages extending therefrom from the inlet or outlet proximal side of the carrier and opening the passage to the fluid flow therethrough. have. The passageway, which is substantially straight from the fluid inlet to the fluid outlet, is defined by a wall coated with the catalyst material with "wash coating" so that gas flowing through the passage is in contact with the catalyst material. The flow path of the single crystal carrier is a thin walled channel that can be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, hexagonal, ellipse, circle. The structure may include from about 60 to about 600 or more gas inlet openings (“cells”) per square inch of cross section. The ceramic carrier may be any suitable refractory material such as cordierite, cordierite-alpha alumina, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, silimite, manganese silicate, Zircon, Petarite, Alpha Alumina and Aluminosilicate. The metallic honeycomb may be made of a refractory material such as stainless steel or other suitable iron based on erosion resistant alloys.

The substrate may comprise a single crystal honeycomb comprising a plurality of parallel channels extending from the inlet to the outlet. The single crystal may be selected from the group consisting of ceramic single crystal and metallic single crystal. The honeycomb can be selected from the group comprising flow-through single crystals and wall flow single crystals. The single crystal carrier may comprise up to about 700 or more flow channels (“cells”) per square inch of cross section, although fewer may be used. For example, the carrier may have about 60 to 600, more typically about 200 to 400 cells per square inch ("cpsi"). Sulfur tolerant catalyst composites generally have a catalyst composition of from about 0.50 g / in ³ to about 6.0 g / in ³ , preferably from about 1.0 g / in ³ to about 5.0 g / in ³ (in grams of compound per volume of single crystal). Base layer) on a single crystal substrate.

The present invention includes a method comprising passing an inlet end fluid comprising an inlet end coating composition to such a substrate. For the purposes of the present invention, fluids include liquids, slurries, solutions, suspensions and the like. The aqueous liquid passes through the channel inlet, extends at least a portion of the length from the inlet end to the outlet end to form an inlet end layer coating, and at least one inlet end coating extends in length portion from the inlet end to the outlet end. A void is applied at the outlet end, but gas flows through the channel from the inlet end after formation of each inlet end coating without significantly changing the length of each inlet layer coating. At least one outlet end aqueous fluid comprising at least one outlet end coating composition passes through the at least some channel outlet at the substrate outlet end to the substrate. The aqueous liquid passes through the channel and extends for at least a portion of the length from the outlet end to the inlet end to form one or more outlet end layer coatings. The method further includes applying a void to the inlet end through which the gas stream passes through the channel after formation of each outlet end coating without significantly changing the length of each outlet layer coating.

The method further comprises a noble metal component selected from the noble metal component of the inlet layer and the noble metal component of the outlet layer from the inlet refractory oxide and the inlet rare earth metal oxide component and the individual inlet or exhaust component selected from the exhaust refractory oxide and the exhaust rare earth metal oxide component. Fixing to the. Fixation may be performed prior to coating the inlet and outlet layers. The fixing step may comprise chemically immobilizing the noble metal component on the individual refractory oxide and / or the rare earth metal oxide. Alternatively, the fixing step may comprise thermally treating the precious metal component on the individual refractory oxide and / or rare earth metal oxide. The fixing step involves calcining the precious metal component on the individual refractory oxide and / or rare earth metal oxide. The calcination step may be carried out at 200 ° C., preferably at 250 ° C. to 900 ° C. for 0.1 to 10 hours. The step of thermally fixing each layer is preferably carried out after coating and prior to coating the subsequent layer. Thermally treating the substrate is completed by corning all layers at 200 ° C. to 400 ° C. for 1 to 10 seconds. The calcination step is preferably carried out on the substrate carried out upon completion of the coating of all the layers. The calcination step is carried out at 250 ° C. to 900 ° C. for 0.1 to 10 hours.

Preferably, the noble metal can be fixed in advance on the support. Alternatively, the method may further comprise fixing the soluble component in the layer, such as one precious metal component, to one of the refractory oxide or the rare earth metal oxide component, wherein the fixing is performed prior to coating the layer. The fixing step may include chemically immobilizing the noble metal on the individual refractory oxide and / or the rare earth metal oxide. More preferably, the fixing step comprises thermally treating the noble metal on the refractory oxide and / or the rare earth metal oxide. The thermal treatment consists in coating the substrate on one or more layers for 1 to 10, preferably 2 to 6 seconds at 200 ° C to 400 ° C. Heat is provided by applying a gas stream, preferably air heated to 200 ° C to 400 ° C. The temperature range has been found to substantially fix soluble components such as precious metal components. The combination of flow rate and gas temperature should be sufficient to heat the coating layer and preferably provide a minimum amount of heat to the underlying substrate to allow for rapid cooling in subsequent cooling steps prior to application of subsequent layers. Preferably, the step of thermally fixing each layer, preferably followed by cooling to ambient temperature, is carried out after coating and prior to coating the subsequent layer. The cooling step is preferably carried out using air at moderate flow rates, typically at 5 ° C.-40 ° C. for 2-20, preferably 4-10 seconds. The combination of air flow rate and temperature of the gas stream should be sufficient to cool the coating layer. The method makes it possible to coat the plurality of layers on a substrate to form the article of the invention. Preferred methods include the step of fixing the precious metal component to the refractory oxide and the rare earth metal oxide component, wherein the fixing is carried out prior to coating the first and second layers.

In another embodiment, the method involves applying a vacuum to the partially impregnated substrate at a strength and time sufficient to elevate the coating medium from the bath to a predetermined distance from each bath to a uniform coating profile for each impregnation step. Steps. Optionally, and preferably, the substrate can be changed to repeat the coating method from the opposite end. The coated substrate must be thermally fixed after forming the layer.

The method may comprise a final calcination step. This can be done between the coating layers or in an oven after the coating of all the layers on the substrate is completed. Calcination may be performed at 250 ° C. to 900 ° C. for 0.1 to 10 hours, preferably at 450 ° C. to 750 ° C. for 0.5 to 2 hours. After all layers have been coated, the substrate can be calcined.

A method aspect of the present invention is a gas containing a hazardous component by converting at least a portion of each of the harmful components including at least one carbon monoxide, hydrocarbon, and nitrogen oxide present initially into harmless substances such as water, carbon dioxide and nitrogen. Provides a way to handle it. The method comprises contacting a gas with the catalyst composition as described above under conversion conditions (eg, an inlet gas of about 100 ° C. to 950 ° C. with respect to the catalyst composition).

In a specific embodiment, the present invention relates to a phase having a hematite composition and structure (test 7). The material consists of iron oxide, aluminum oxide and small amounts of yttrium oxide and strontium oxide. The iron oxide phase is not completely consistent with hematite. The diffraction pattern does not match completely and slight shifts are observed at the peak position when compared to the control pattern of hematite. Changing the structure makes a change in manipulating the physical and / or catalytic properties of the simple oxides. Small differences in composition or structure can cause changes in these properties or develop new ones. One example may be the creation of a polarizing structure in BaTiO ₃ that imparts variable dielectric properties by twisting from a cubic to square structure. This manipulation focuses on determining whether small structural changes can be measured with small changes in lattice constants. For this purpose, accurate measurement of unit cell constants is required. It is also important to know the errors associated with the measurements in order to know when the two measured passion parameters are quite different.

Hematite is basically a six-cell cell. XRD data were collected using White Rock 10 μm quartz as an internal standard for NIST Sibley Ore samples to determine unit cell parameters (test D20327). XRD data for the experimental samples (Experiment 7) were also collected using the same method. These data sets were adjusted to obtain unit cell parameters a _o and c _o . The results are tabulated in conjunction with the following ICDD data, reference card numbers 33-664.

Sample a _o (A) c _o (A) Test 7 5.00821 (0.001166) 13.69433 (0.002883) Experimental NIST Hematite Standard 5.03453 (0.002828) 13.75294 (0.00009) ICDD 5.036 13.749 No standard deviation given Reference 33-664

The a _o and c _o values of the NIST hematite standard samples closely matched those of the ICDD hematite reference cards 33-664, but no standard deviation was given to the ICDD card. Close agreement of the experimental data with that of ICDD strongly indicates that data collection and adjustment is acceptable. Thus, an effective comparison between the cell parameters of Sample Test 7 and the cell parameters of NIST hematite samples can be determined to determine whether the crystal structure of Experiment 7 is truly different from standard hematite.

The lattice parameters for phase with hematite-like structure in Experiment 7 are a _o = 5.00821 (0.001166) 'and c _o = 13.69433 (0.002883)'. Comparing these lattice constants with those of hematite obtained from NIST (measured experimentally) indicates that they are different. The difference is outside the experimental error range. This difference may be due to the impurity atoms present in the crystal sites or the gap sites. At present, the type or position of these impurity atoms is not measurable.

In a preferred embodiment, the present invention

(1) providing a catalyst composite;

(2) an adsorbent through which a lean gaseous stream comprising NOx and SOx is passed through the catalyst complex within the adsorption temperature to adsorb at least some NOx contaminants to provide a NOx depleted gaseous stream exiting the catalyst complex, Adsorbing and mitigating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite;

(3) in the NOx desorption and alleviator, converting the lean gaseous stream into a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to provide a reduced NOx rich gaseous stream exiting the catalyst complex. step;

(4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream,

Wherein the catalyst complex is

(a) a platinum component;

(b) a support; And

(c) i) up to about 0.1% Na ₂ O;

ii) about 1% or less of MgO;

iii) about 10% to about 30% Fe ₂ O ₃ ;

iv) about 0.5% to about 15% SrO;

v) up to about 5% Y ₂ O ₃ ; And

vi) Al ₂ O ₃ components remaining from the NOx adsorbent composite,

(i) providing an aqueous suspension or solution of the NOx adsorbent component composition;

(ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And

(iii) a NOx adsorbent composite prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor.

A method for removing NOx contaminants from an SOx containing gaseous stream, comprising:

In another preferred embodiment, the present invention

(a) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor;

(iii) separating the precipitate from the mother liquor; And

(iv) a catalyst composite prepared by a hydrothermal synthesis method comprising the step of forming a mixture of precipitate, platinum component, and support.

In another preferred embodiment, the present invention

(a) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor;

(iii) separating the precipitate from the mother liquor; And

(iv) forming a mixture of precipitate, platinum component, and support.

In another preferred embodiment, the present invention

In another preferred embodiment, the present invention

(1) (a) a support; And

(b) (i) up to about 0.1% Na ₂ O;

(ii) up to about 1% MgO;

(iii) about 10% to about 30% Fe ₂ O ₃ ;

(iv) about 0.5% to about 15% SrO;

(v) up to about 5% Y ₂ O ₃ ; And

(vi) forming a mixture of NOx adsorbent components comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite;

(2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid;

(3) forming a layer of a solution or dispersion on the substrate; And

(4) converting the platinum component in the obtained layer to a water insoluble form,

Where the NOx adsorbent component is

(i) providing an aqueous suspension or solution of the NOx adsorbent component composition;

(ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And

(iii) a method of forming a catalyst composite, which is prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor.

In this preferred embodiment, the NOx adsorbent component may further comprise BaO in an amount of about 0.5% to about 15%.

The following examples further illustrate various embodiments of the present invention and are provided to provide a comparison between the listed catalysts of the present invention and prior art catalysts. The examples are provided to illustrate the nature of the claims method and are not intended to limit the scope of the claims. Unless otherwise indicated, parts and percentages in the examples are parts by weight and weight percent.

Preparation of Sulfur Tolerant NOx Trap Material

Example 1 (E1)

The following precursors were weighed: 1422.02 g of aluminum acetate Al-Ac (containing boehmite, AlOOH, 65.4 wt.% Al ₂ O ₃ ); 625 g of barium acetate Ba-Ac (containing 60% by weight BaO); Cerium nitrate aqueous Ce-N solution (containing 30.6 wt.% CeO ₂ ) 637.2 g.

Barium acetate was first dissolved in deionized water. Cerium nitrate was also dissolved in deionized water. The solution had a pH of 7.62. Al-Ac was added to the Ba-Ac solution with continuous stirring. Deionized water was added and the final slurry had a pH of 6.32. Cerium nitrate solution was added to the slurry. Mixing was continued for 1 hour and the pH dropped to 5.75. The slurry began to gel. Mixing lasted overnight and the gel thickened like jelly. Additional deionized water was added to the gel to dilute and the total volume was 12 L. The gel was transferred to a 5 gallon autoclave for hydrothermal synthesis.

The autoclave was heated to 232 ° C. and maintained at 232 ° C. for 2 hours, then cooled to room temperature. It was immersed at room temperature for 60 hours and the autoclave was heated to 230 ° C. The hydrothermal method was continued for 48 hours at 230 ° C. and then cooled to room temperature.

The product was centrifuged. The mother liquor had a pH of 4.68. The precipitate was washed with deionized water and centrifuged again. The product was dried overnight and calcined in a box heater at 550 ° C. for 2 hours. The final product had a BET surface area of 62 m ² / g. Semiquantitative XRF analysis of the final complex of Al ₂ O ₃ 84.7% by weight - shows that BaO of 2.4% by weight - 11.5% by weight of CeO _2.

Example 2 (E2)

Trap material E2 was prepared by hydrothermal synthesis and made as follows. The following precursors were weighed. 45.04 g of aluminum acetate Al-Ac (containing boehmite, AlOOH, 65.4 wt.% Al ₂ O ₃ ); 44.59 g of cobalt nitrate Co-N (containing 22.5 wt.% CoO); And 34.135 g of lanthanum nitrate La-N solution (containing 27.1 wt.% La ₂ O ₃ ).

Co-N was dissolved in the La-N solution and deionized water was added to completely dissolve the Co salt. The final solution had a pH of 1.23. Al-Ac was added to 250 g of deionized water under constant stirring. The slurry had a pH of 5.29. The nitrate solution was added to the slurry under vigorous stirring. Gradually the mixed slurry began to gel. At this stage, the measured pH was 4.96. 10% concentration of ammonia was added dropwise until the pH was increased to 7.60 and the color of the gel turned bluish green. The gel was transferred to the autoclave. Hydrothermal synthesis was performed at 250 ° C. for 64 hours. The product was washed and centrifuged, then dried and calcined at 550 ° C. for 2 hours. 79% by weight of a semi-quantitative XRF Al ₂ O ₃ - 19 wt% Co ₃ O ₄ - 1% by weight La ₂ O ₃ was obtained.

Example 3 (E3)

Samples were prepared by hydrothermal synthesis. The composition of the sample (XRF) 25.2 wt.% BaO - 11.0 wt.% CeO ₂ - 63.8 was wt% Al ₂ O _3.

Example 4 (E4)

Samples were prepared by hydrothermal synthesis. The composition of the sample is 25% by weight SrO - was 43 wt% Al ₂ O ₃ - 32 wt% TiO _2.

Example 5 (E5)

This is a sample whose composition is the same as in Example 3, but not prepared by hydrothermal synthesis. Example 5 was prepared by co-precipitation. Precursor cerium nitrate (39.63 wt% CeO ₂ ), barium acetate (60.6 wt% BaO), aluminum acetate (65.5 wt% Al ₂ O ₃ ) was used. Al-Ac was added to the Ba-Ac aqueous solution under vigorous stirring to prepare a slurry. Acetic acid was added dropwise to the slurry. The pH was reduced to 6-5, and the slurry began to gel. Ce-N solution was added to the gel under stirring. Acetic acid was added and the pH was close to 5. The gel was transferred to a crucible and dried at 150 ° C. overnight. The dried material was lowered and sieved to 250 um. The granules were calcined at 300 ° C. for 4 hours and then at 450 ° C. for 6 hours.

Preparation of Trap Test Samples for Small Reactors

Examples of NOx Trap Test Samples (Samples T1 to T5)

Sample Preparation: Cationic Pt solution was injected into the materials (E1 to E5) to obtain a 1% by weight Pt loading dispersed on the trap material. The injected sample was dried and calcined at 450 ° C. for 1 hour to obtain a dry mass. The mass was crushed and sieved to obtain particles with an average diameter of 300 um grains. Thus, trapping test materials corresponding to trap materials E1 to E5 were obtained and designated as T1 to T5, 300 um granule particles loaded with 1% by weight Pt.

Test Method of NOx Trapping and Sulfur Regeneration

Test protocol and CO injection method

Traps were trapped with NOx and SOx using a lean gas stream, NOx (and SOx) were released using rich flow and sulfur was recovered from the sample. The tuning valve was used to open and close the O2 / CO gas line simultaneously to inject CO (or vice versa).

O2 NO CO N2 SO2 rich 0 500 ppm 2.2% balance 60 ppm Lynn 10% 500 ppm 0 balance 60 ppm

Lean / Rich cycles were set to Lean for 5 minutes and Rich for 5 seconds alternately with VHSV 50,000 / hr or 25,000 / hr.

Note that high concentrations of SOx (60 ppm) were used in this test. State-of-the-art commercial diesel fuel containing 350 ppm can produce 20 ppm SO 2 in the exhaust gas stream. Thus, the 60 ppm SOx level used in this test is three times what would be expected for a modern commercial diesel fuel.

NOx and SOx baselines were first measured using empty tubes prior to testing. Samples of trap material were loaded in a reactor tube with a 50:50 mixture with cordierite particles. In an alternating lean / rich scheme, NO levels as a function of sulfur deactivation and regeneration were observed and recorded.

After the start of the experiment, the NO level in the catalyst effluent gradually increases over time as more and more sulfur is adsorbed on the NO x trap. Degeneration of the NO conversion indicates that the NOx trap grade is deactivated in the SOx environment. The degenerated NOx trap was then regenerated at a given temperature. Subsequently, observation and recording of NOx trap performance were repeated. Good recycled NOx traps should exhibit the same NO conversion level as not deactivated.

Unless otherwise specified, NOx performance tests were performed at a constant temperature of 300 ° C.

Test Methods

Samples were aged in air (oven) for 2 hours at 700 ° C. prior to testing.

NOx and SOx baselines were measured without catalyst first in the reactor prior to running the sample.

Test tube loading: Sample T2 was loaded in the reaction tube with mixed (100 mg trap material) + (100 mg cordierite, diluent); Other samples (50 mg trap material) + (50 mg cordierite); Total gas flow was 100 sccm. VHSV: 25,000 / hr for T2, equivalent 200 g / (ft) ³ Pt loading, VHSV: 50,000 / hr, equivalent 100 g / (for other samples (T1, T3, T4 and T5) ft) There was a ³ Pt loading.

A lean / rich cycle was performed for 2 hours at a constant temperature of 300 ° C. and the level of NO change was recorded. If the catalyst is deactivated by S, the NOx level should be gradually increased. The NOx / SOx trap was then regenerated for 15 minutes at a given temperature (eg 450 ° C, 500 ° C, 550 ° C). After regeneration of S, the NOx trap function was retested. The original level and NOx level were compared to evaluate the regeneration efficiency.

Outcome 1 Performance comparison of sulfided and regenerated lean / rich method NOx trap samples

% NO conversion is shown in the following table. Higher% NO conversion indicates more efficient NOx trap performance, and lower% NO indicates lower efficiency NOx trap due to reduced activity by sulfur and / or low recovery by regeneration process.

% NO conversion-deactivation by SO2 and recovery after regeneration

Sample A A ' B C D play T1 (E1) 68% - 46% - 68% 400 ℃ T2 (E2) ^* 75% - 74% 73% 77% 400 ℃ T3 (E3) 58% - 46% - 70% 550 ℃ T4 (E4) 77% - 68% - 77% 500 ℃ T5 (E5) 31% 19% - - - ^** cannot be regenerated at 550 ° C

^* 100 mg loading (25,000 VHSV)

^** T5 has the same composition as T3 but was not synthesized by hydrothermal synthesis. T5 was prepared by the coprecipitation method. T5 had much lower NOx conversion activity than T3. It was also found that T5 could not be regenerated at 550 ° C.

A: Initial NO conversion of new sample without sulfur

A ': Exposure to 60 ppm SO ₂ for 15 minutes.

B: exposed to 60 ppm SO ₂ for 1 hour.

C: exposed to 60 ppm SO ₂ for 2 hours.

D: After playing for 15 minutes.

Result 2 Continuous NOx trapping performance for extended periods in sulfur environments without regeneration

Sample T2 was exposed to 60 ppm SO ₂ for an extended period of time. After 22 hours, the NO conversion level remained at 49%. At 300 ° C. operating temperature, sulfur could be partially regenerated, so the NOx trap T2 remained active (low level). In this regard, T2 was a sulfur tolerant NOx trap.

Example 6 (E6)

This example shows a NOx trap sample prepared using Fe as one of the important elements. The results of the model gas reactors clearly showed that the sample can partially regenerate sulfur at 300 ° C. operating temperature and at the same time perform a NOx trap function. The NOx trap is a sulfur tolerant NOx trap, which can practically maintain a certain amount of NOx activity without time limit.

45.04 g aluminum acetate Al-Ac (65.5 wt% Al ₂ O ₃ ), 55.80 g iron nitrate Fe-N (14.0 wt%, Fe), and 34.14 g lanthanum nitrate La-N solution (27.1 wt% La ₂ O ₃ ) precursors were weighed. Iron nitrate was dissolved in the lanthanum nitrate solution. A slurry of Al-Ac was prepared with 200 g of deionized water. The slurry was stirred continuously for 2 hours, which began to gel. The nitrate solution was added to the Al-Ac slurry. A dark brown gel formed. The gel was aged overnight. The measured pH was 3.5. The aged gel was hydrothermally treated at 250 ° C. for 72 hours. The precipitate was separated from the mother liquor, washed once and dried overnight. The mother liquor had a pH <3.

Preparation of Test Samples for Small Reactors

Example T6

The same test sample preparation method was used to prepare T6. T6 was prepared from E6, having a granule form of 300 um diameter and loaded with 1 wt% Pt.

Test result

The test method was the same as that used in T1 to T5, using 50 mg sample loading and 50,000 / hr VHSH. In a 60 ppm SO ₂ environment, the initial NO conversion was 57%, then decreased to 47% after 1 hour and 50% after 2 hours. However, the initial activity increased to 70% after 500 ° C. regeneration. After a long continuous test, the trap still showed NOx activity. After 68 hours the NO conversion was 47%. Given that the amount of SO ₂ flowing through is about 1 mg per hour (calculated), 68 mg of SO ₂ was passed through a 50 mg sample for 68 hours. This clearly shows that the sample can partially regenerate sulfur at 300 ° C. operating temperature and also perform the NOx trap function at the same time. NOx trap T6 was a sulfur tolerant NOx trap and was able to maintain a certain amount of NOx activity substantially without time limitation. Sulfur regeneration time was quite low. After 68 hours of continuous testing, NOx activity was restored to 400 ° C. sulfur regeneration.

Example 7

Test 7 was manually polished in mortar and mortar. White Rock 10 μ quartz was added as an internal standard and the two powders were homogenized. The mixture was then packed back into the plate voids. X-ray diffraction data were collected using a Philips vertical protractor set at 45 kV and 40 mA. The scan range was 20 ° to 90 ° 2θ using a step size of 0.02 ° 2θ and a 10 second count time per step. Tests include phase close structures for boehmite, transitional alumina and hematite. An internal standard quartz is also present, see spectrum below. Peaks corresponding to those of the quartz internal standard were first profile-fitted to determine the peak center and intensity. The unit cell was adjusted using the profile fitting peak position, the hkl representation of each peak and the spatial group for hematite, R-3c. Initial lattice parameters were obtained from reference cards 33-664. To confirm this, operational data were collected against the NIST iron ore standard consisting predominantly of hematite. Trace amounts of quartz and maghemite were also present. The test number of this sample was D20328N. The scan range was 19 ° to 86 ° 2θ using a step size of 0.02 ° 2θ and a 10 second count time per step. White Rock 10 μ quartz was used as internal standard. Raw data was processed in the same manner as in test 7.

Although the invention has been described in detail in connection with specific embodiments thereof, the embodiments are exemplary and the scope of the invention is defined in the appended claims.

Claims (46)

(1) providing a catalyst composite; (2) In the adsorber, a lean gaseous stream comprising NOx and SOx is passed through the catalyst complex within the adsorption temperature to adsorb at least a portion of the NOx contaminants and to exhaust the NOx depleted gaseous stream exiting the catalyst complex. Providing and absorbing and alleviating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite; (3) During the NOx desorption and alleviation, a reduced NOx rich gaseous stream is converted to a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to exit the catalyst complex. Providing a; (4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream, Wherein the catalyst complex is (a) a platinum component; (b) a support; And (c) (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts which, when hydrolyzed, produce metal oxides respectively; (ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; And (iii) is prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor, The metal in the first metal oxide is selected from aluminum, titanium, zirconium, silicon and composites thereof, and the metal in the second metal oxide is from group IIA metals, group III metals, group IV metals, rare earth metals and transition metals. Wherein the metal in the first metal oxide comprises a NOx adsorbent component comprising a first metal oxide and a second metal oxide, different from the metal in the second metal oxide, A process for removing NOx contaminants from a SOx containing gaseous stream. The process of claim 1 wherein the SOx desorption temperature range of (4) is about 300 ° C. or greater. The process of claim 2 wherein the SOx desorption temperature range of (4) is at least about 350 ° C. 4. The method of claim 3, wherein the SOx desorption temperature range of (4) is at least about 400 ° C. 5. The method of claim 4, wherein the SOx desorption temperature range of (4) is at least about 450 ° C. 6. The method of claim 1 further comprising a platinum group metal component other than platinum. The method of claim 6 wherein the platinum group metal component is selected from the group consisting of palladium, rhodium, ruthenium and iridium components and mixtures thereof. The method of claim 1 wherein the support is selected from the group consisting of alumina, silica, titania and zirconia compounds. The process of claim 1 wherein the support is activated alumina, alumina-ceria, alumina-chromia, alumina-zirconia, silica, silica-titania, silica-titania-alumina, silica-titania-zirconia, titania, zirconia, zirconia-titania and Zirconia-alumina-titania. The method of claim 1, wherein the metal in the second metal oxide is magnesium, calcium, strontium, barium, scandium, titanium, zirconium, hafnium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, Erbium, thulium, ytterbium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. The method of claim 10, wherein the metal in the second metal oxide is selected from the group consisting of barium, lanthanum, cerium, iron, cobalt, and copper. The method of claim 1 wherein the metal in the first and second metal oxides is selected from the group consisting of aluminum / cerium / barium, aluminum / copper / lanthanum, aluminum / cobalt / lanthanum and iron / aluminum. The method of claim 1, wherein the metal in the first metal oxide and the metal in the second metal oxide are each present in a molar ratio of about 3: 7 to about 9: 1. The method of claim 13, wherein the metal in the first metal oxide and the metal in the second metal oxide are each present in a molar ratio of about 4: 6 to about 8.5: 1.5. The method of claim 1 wherein the catalyst composite (i) at least about 1 g / ft ^{3 of} platinum component; (ii) from about 0.15 g / in ³ to about 6.0 g / in ^{3 of the support} ; And (iii) from about 0.025 g / in ³ to about 4 g / in ³ of the NO x adsorbent component. The process of claim 1 wherein the precursors of the first metal oxide and the second metal oxide are from the group consisting of acetate, nitrate, hydroxide, oxychloride, hydroxychloride, carbonate, sulfate, oxalate and tartrate The water-soluble / dispersible metal salt of choice. The method of claim 1, wherein a temperature of about 175 ° C. to about 250 ° C. is added to the suspension or solution of the metal hydroxide of 4 (c) (ii). The method of claim 1, wherein the precipitate of 4 (c) (ii) has an average particle size of about 0.01 to about 0.2 microns. The method of claim 1, wherein the catalyst composite is supported on a metal or ceramic honeycomb carrier or is pressed independently. The method of claim 1, wherein the NOx adsorbent component further comprises a third metal oxide, wherein the metal in the third metal oxide is selected from aluminum, titanium, zirconium, silicon and composites thereof, wherein the metal in the second metal oxide is The group IIA metal, group III metal, group IV metal, rare earth metal and transition metal, wherein the metal in the third metal oxide is different from the metal in the second metal oxide. (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively; (ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; (iii) separating the precipitate from the mother liquor; And (iv) forming a mixture of precipitate, platinum component, and support Catalyst composite prepared by hydrothermal synthesis comprising a. The catalyst composite of claim 21 further comprising mixing a platinum group metal component other than platinum in step (iv). The catalyst composite of claim 21 wherein the platinum group metal component is selected from the group consisting of palladium, rhodium, ruthenium and iridium components and mixtures thereof. The catalyst composite of claim 21 wherein the support in (iv) is selected from the group consisting of alumina, silica, titania and zirconia compounds. The method of claim 21, wherein the support in step (iv) is activated alumina, alumina-ceria, alumina-chromia, alumina-silica, alumina-zirconia, silica, silica-titania, silica-titania-alumina, silica-titania-zirconia , A catalyst composite selected from the group consisting of titania, zirconia, zirconia-titania, and zirconia-alumina-titania. The method of claim 21, wherein the metal in the second metal oxide is magnesium, calcium, strontium, barium, scandium, titanium, zirconium, hafnium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, A catalyst composite selected from the group consisting of erbium, thulium, ytterbium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. 27. The catalyst composite of claim 26 wherein the metal in the second metal oxide is selected from the group consisting of barium, lanthanum, cerium, iron, cobalt and copper. The catalyst composite of claim 21 wherein the metal in the first and second metal oxides is selected from the group consisting of aluminum / cerium / barium, aluminum / copper / lanthanum, aluminum / cobalt / lanthanum and iron / aluminum. The catalyst composite of claim 21, wherein the metal in the first metal oxide and the metal in the second metal oxide are each present in a molar ratio of about 3: 7 to about 9: 1. 30. The catalyst composite of claim 29 wherein the metal in the first metal oxide and the metal in the second metal oxide are each present in a molar ratio of about 4: 6 to about 8.5: 1.5. The method of claim 21, wherein the catalyst composite is (i) at least about 1 g / ft ^{3 of} platinum component; (ii) from about 0.15 g / in ³ to about 6.0 g / in ^{3 of the support} ; And (iii) a catalyst composite comprising from about 0.025 g / in ³ to about 4 g / in ³ of the NO x adsorbent component. The method of claim 21 wherein the precursors of the first metal oxide and the second metal oxide are from the group consisting of acetate, nitrate, hydroxide, oxychloride, hydroxychloride, carbonate, sulfate, oxalate and tartrate A catalyst composite that is the water soluble / dispersible metal salt of choice. The catalyst composite of claim 21, wherein the catalyst composite is subjected to a temperature of about 175 ° C. to about 250 ° C. to the suspension or solution of the metal hydroxide of (ii). The catalyst composite of claim 21, wherein the precipitate of step (ii) has an average particle size of about 0.01 to about 0.2 microns. The catalyst composite of claim 21, wherein the catalyst composite is supported on a metal or ceramic honeycomb carrier or is pressed independently. The method of claim 21, wherein the NOx adsorbent component further comprises a third metal oxide, wherein the metal in the third metal oxide is selected from aluminum, titanium, zirconium, silicon and composites thereof, wherein the metal in the second metal oxide is The catalyst composite is selected from the group consisting of Group IIA metals, Group III metals, Group IV metals, rare earth metals, and transition metals, wherein the metal in the third metal oxide is different from the metal in the second metal oxide. (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively; (ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Adding a temperature of; (iii) separating the precipitate from the mother liquor; And (iv) forming a mixture of precipitate, platinum component, and support. (1) (a) a support; And (b) forming a mixture of NOx adsorbent components; (2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid; (3) forming a layer of a solution or dispersion on the substrate; And (4) converting the platinum component in the obtained layer to a water insoluble form, Where the NOx adsorbent component is (i) providing an aqueous suspension or solution of the first and second metal oxides or precursors of the first and second metal oxides, or both, which are metal salts that, when hydrolyzed, produce metal oxides respectively; (ii) from about 150 ° C. to about 300 ° C. in a suspension or solution of the first and second metal oxides or their precursors in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor. Applying a temperature of; And (iii) a method of forming a catalyst composite, prepared by a hydrothermal synthesis method comprising separating the precipitate from the mother liquor. (1) providing a catalyst composite; (2) the adsorber passes a lean gaseous stream comprising NOx and SOx through the catalyst complex within the adsorption temperature to adsorb at least some NOx contaminants to provide a NOx depleted gaseous stream exiting the catalyst complex, Adsorbing and mitigating at least some of the SOx contaminants in the gaseous stream to provide an SOx depleted gaseous stream exiting the catalyst composite; (3) in the NOx desorption and alleviator, converting the lean gaseous stream into a rich gaseous stream to reduce and desorb at least some NOx contaminants from the catalyst complex to provide a reduced NOx rich gaseous stream exiting the catalyst complex. step; (4) In the SOx desorber, convert the lean gaseous stream into a rich gaseous stream and raise the temperature of the gaseous stream to within the desorption temperature to reduce and desorb at least some of the SOx contaminants from the catalyst complex to regenerate the catalyst complex and Providing an exiting reduced SOx-rich gaseous stream, Wherein the catalyst complex is (a) a platinum component; (b) a support; And (c) i) up to about 0.1% Na ₂ O; ii) about 1% or less of MgO; iii) about 10% to about 30% Fe ₂ O ₃ ; iv) about 0.5% to about 15% SrO; v) up to about 5% Y ₂ O ₃ ; And vi) Al ₂ O ₃ components remaining from the NOx adsorbent composite, (i) providing an aqueous suspension or solution of the NOx adsorbent component composition; (ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And (iii) a NOx adsorbent composite prepared by a hydrothermal synthesis method comprising the step of separating the precipitate from the mother liquor. And removing NOx contaminants from the SOx containing gaseous stream. The method of claim 39, wherein the NO x adsorbent component further comprises about 0.5% to about 15% BaO. (a) up to about 0.1% Na ₂ O; (ii) up to about 1% MgO; (iii) about 10% to about 30% Fe ₂ O ₃ ; (iv) about 0.5% to about 15% SrO; (v) up to about 5% Y ₂ O ₃ ; And (vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite; (b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; (c) separating the precipitate from the mother liquor; And (d) forming a mixture of precipitate, platinum component, and support Catalyst composite prepared by hydrothermal synthesis comprising a. The method of claim 41, wherein the NO x adsorbent component further comprises about 0.5% to about 15% BaO. (a) up to about 0.1% Na ₂ O; (ii) up to about 1% MgO; (iii) about 10% to about 30% Fe ₂ O ₃ ; (iv) about 0.5% to about 15% SrO; (v) up to about 5% Y ₂ O ₃ ; And (vi) providing an aqueous suspension or solution of the NOx adsorbent component comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite; (b) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; (c) separating the precipitate from the mother liquor; And (d) forming a mixture of precipitate, platinum component, and support Method for producing a catalyst composite comprising a. The method of claim 43, wherein the NO x adsorbent component further comprises about 0.5% to about 15% BaO. (1) (a) a support; And (b) (i) up to about 0.1% Na ₂ O; (ii) up to about 1% MgO; (iii) about 10% to about 30% Fe ₂ O ₃ ; (iv) about 0.5% to about 15% SrO; (v) up to about 5% Y ₂ O ₃ ; And (vi) forming a mixture of NOx adsorbent components comprising Al ₂ O ₃ components remaining of the NOx adsorbent composite; (2) combining the water soluble or dispersible platinum component and the mixture obtained from step (1) with an aqueous liquid to form a solution or dispersion sufficiently dry to absorb substantially all of the liquid; (3) forming a layer of a solution or dispersion on the substrate; And (4) converting the platinum component in the obtained layer to a water insoluble form, Where the NOx adsorbent component is (i) providing an aqueous suspension or solution of the NOx adsorbent component composition; (ii) applying a temperature of about 150 ° C. to about 300 ° C. to a suspension or solution of the NOx adsorbent component composition in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size of about 0.001 to 0.2 microns in the mother liquor; And (iii) a method of forming a catalyst composite, prepared by hydrothermal synthesis comprising the step of separating the precipitate from the mother liquor. 46. The method of claim 45, wherein the NOx adsorbent component further comprises about 0.5% to about 15% BaO.